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ASE BRAKES A5 TEST EXAMS | QUESTIONS AND CORRECT ANSWERS WITH RATIONALES| ALREADY GRADED A+ | VERIFIED ANSWERS | LATEST VERSION 2024-2025 Ona car with disc/drum brakes, the front brakes grab quickly when light pedal pressure is applied. This problem could be caused by a bad: A. Proportioning valve B. Pressure safety switch C. Metering valve D. Residual check valve - ANSWER-The correct answer is C. The metering valve delays the flow of brake fluid to the front calipers until the pressure in the system rises to a point where the wheel cylinder can overcome the tension of the brake shoe returning spring. The purpose is to have both front and rear brakes apply simultaneously. This prevents the front brakes from locking up during light brake applications. The driver of a vehicle with power disc/drum brakes says that the brake pedal moved slowly to the floor while maintaining pedal pressure at a stoplight. What could cause this problem? A. Leaking primary piston cup in master cylinder B. Leaking power brake booster C. Leaking residual check valve in master cylinder D. Internal leak in the combination valve - ANSWER-The correct answer is A. if the primary piston cup in the master cylinder is leaking, pressure will not build up ahead of the primary piston to increase pressure to the rear brakes. The piston will then move forward until the spring is compressed enough to move the secondary piston. Consequently, this internal leak will cause the brake pedal to slowly drop to the floor. What is the purpose of the master cylinder residual check valve(s) on vehicles equipped with drum brakes? A. Allowed the driver to pump up the brakes B. Prevents air from entering the hydraulic system C. Prevents wheel lockup by reducing the hydraulic pressure D. Reduces pedal pulsation by controlling hydraulic pressure - ANSWER-The correct answer is B. Residual check valve(s) are used on drum brakes to keep residual low pressure (slight static pressure) in the brake system at all times even when the brake pedal is released. This pressure (5-20 psi) keeps the lips of the wheel cylinder piston cups tight against the cylinder walls to prevent air from entering the system when at rest (brakes released). A technician has just overhauled the front brakes on a vehicle with front disc and rear drum brakes. However, when he attaches a pressure bleeder (pressurized to about 25 psi) to the master cylinder, he cannot get any fluid to come out of the disc brake caliper bleeder screws. Which of the following is MOST LIKELY the cause? A. Bad proportioning valve B. Bad pressure differential valve C. proportioning valve release button not activated D. Metering valve release button not activated - ANSWER-The correct answer is D. A metering valve requires a minimum pressure (typically 75-125 psi) to open. At this point pressurized fluid flows to the front calipers. Since the bleeder tank is only pressurized to 25 psi, fluid pressure is too low to open the metering valve during this procedure, Therefore, when you use a pressure bleeder on a system with a metering valve, you must manually keep the valve open by either pushing the button in the end of the valve, or pulling the stem outward on the end of the valve. Ona vehicle with single piston floating caliper front disc brakes, the brake pads on the left side of the vehicle are almost completely worn while the right side is almost new. Tech A says that too much rotor runout could be the cause. Tech B says that a binding caliper piston could be the cause. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is B. Excessive rotor runout would cause a pulsating brake pedal, but not uneven side-to-side pad wear. A frozen caliper piston on the other hand, will Keep both inner and outer brake pads equally applied against the rotor even when the brake pedal is released. This constant friction will cause rapid pad wear in the affected caliper as well as the front-end pull A hydraulic brake line is leaking. Which of the following is the correct repair procedure? A. Cut out the bad section and replace with new steel tubing using compression fittings. B. Replace the leaking line with double-flared, seamless copper tubing. C. Cut out the bad section and replaced with single-flared steel tubing using flare nuts and unions. D. Replace the leaking line with double-flared steel tubing. - ANSWER-The correct answer is D. Steel tubing of the same size, type, and length with double flared ends must be used when replacing a traditional SAE double inverted flair style hydraulic brake line. Which of the following problems would be caused by using a residual check valve in a disc brake master cylinder? A. Reduced brake pedal travel B. Reduced brake system pressure C. Increased brake pad wear D. Increased rotor runout. - ANSWER-The correct answer is C. If a residual check valve was installed in a disc brake master cylinder, it would cause increased brake pad wear since the residual brake pressure would cause the caliper pistons to keep the pads applied even when the brake pedal is released. sensors under this condition are not in sync with each other, the ABS control unit interprets this as impending wheel lockup and responds by engaging the system. Two technicians are discussing the duo-servo type drum brake design. Technician A says that the brake lining on the secondary shoe is usually thicker than the brake lining on the primary shoe. Technician B says the primary shoe is installed toward the rear of the vehicle. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is A. In a duo-servo drum brake design under normal forward braking, the friction developed by the secondary lining is greater than the primary lining. Therefore, the secondary shoe is typically longer and thicker than the primary shoe. The primary shoe is installed facing the direction of forward motion. All of the following statements about leading-trailing type drum brakes are true EXCEPT: A. The leading shoe does most of the forward braking. B. Both brake shoes are held against a fixed anchor on the back plating. C. They are self-energizing. D. The trailing shoe does most of the reverse braking. - ANSWER-The correct answer is C. The leading-trailing drum brake design is not self-energizing. This is due to the fixed anchor on the backing plate, which prevents the shoe from transferring their force to one another. Technician A says that DOT 5 brake fluid had a lower boiling point than DOT 4. Technician B says that DOT 4 brake fluid is silicone-based and should never be used in an ABS system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is D, neither technician is right. It is DOT 4 brake fluid that has a lower boiling point, and DOT 5 that is silicone-based and should not be used in any ABS system. Brakes that drag or fail to release can be caused by which of the following conditions in the master cylinder? A. leaking primary cup B. leaking secondary cup C. failure of the residual pressure check valve D. clogged compensating port - ANSWER-The correct answer is D. The compensating port allows for residual hydraulic line pressure to be discharged into the reservoir as the brake pedal is released. A clogged or restricted compensating port will create a pressure build-up, which will cause the brakes to drag or fail to release. The port can be clogged by foreign matter, blocked by a swollen primary cup or covered by the primary cup if the master cylinder pushrod is improperly adjusted. All of the following could cause a hard brake pedal on a vehicle with power brakes EXCEPT: A. An engine with the valves adjusted too tight B. Brake fluid on the linings C. A leak in the brake hydraulic system D. A frozen caliper - ANSWER-The correct answer is C. A leak in the hydraulic system wouldn't cause a hard pedal but rather create the exact opposite condition due to the hydraulic pressure loss. An engine with the valves adjusted too tight would develop low vacuum. This would adversely affect the operation of the power brake booster and cause a hard pedal. Brake fluid on the linings will cause the friction material to grab resulting in a hard pedal, while a frozen caliper would prevent retraction of the piston resulting in a similar condition. Technician A says that a caliper seal installed in the caliper bore is called a stroking seal. Technician B says that when the brake pedal is released, the piston in the caliperpves back in its bore due to the action of the piston seal. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is B. The outward movement of the caliper piston during brake application causes the piston seal to distort. Once the brakes are released however, the seal returns to its original shape forcing the piston to retract in its bore. A caliper seal that is installed on the piston is known as a stroking seal. When replacing disco brake pads, you must bottom the caliper piston in its bore to create room for the new pads. Which of the following is proper procedure? A. Use a C-clamp or pliers to slowly bottom the piston in the caliper. B. Remove half the fluid from the master cylinder reservoir, then use a C-clamp or pliers to slowly bottom the piston in the caliper. C. Connect a hose to the caliper bleeder screw and insert the other end of the hose into a suitable container, open the bleeder screw, then use a C-clamp or pliers to slowly bottom the piston in the caliper. D. Remove the caliper from the vehicle, then use a C-clamp or pliers to slowly bottom the piston caliper. - ANSWER-The correct answer is C. By opening the bleeder screw on the caliper, contaminated fluid is not forced back into the master cylinder (or on ABS vehicles, into the hydraulic control unit). Answer B is wrong because, while it will work, doing so could cause problems in the hydraulic system. Answer A is wrong because, without checking the fluid level or opening the bleeder screw, fluid could be forced into and spill out of the master cylinder reservoir. Answer D is wrong because caliper removal is not necessary. Excessive slack in the parking brake cables can be eliminated on most vehicles by making an adjustment at the : A. equalizer B. star wheel adjusters C. strut rod D. pushrod - ANSWER-The correct answer is A. On most vehicles, parking brake adjustment consists of shortening the length of one or more cables to remove excessive slack. This adjustment is generally made by tightening an adjusting nut at the equalizer. A customer complains that the brake warning light comes on whenever the brake pedal is depressed while driving. All of the following could cause the to occur EXCEPT: A. A leak in the rear half of the hydraulic system. B. A short to ground in the warning light circuit. C. A leak in the front half of the hydraulic circuit. D. A leaking pressure differential switch. - ANSWER-The correct answer is B. Any leak in the hydraulic system that causes unequal pressure to be applied to one side of the pressure differential piston will cause the warning light to illuminate. The only choice here is a short to ground in the light. This failure would cause the light to stay on all the time regardless of hydraulic condition. The MOST common cause for premature front brake pad wear in disc/drum system is: A. Seized calipers B. Faulty master cylinder C. Improperly adjusted rear shoes D. Malfunctioning metering valve - ANSWER-The correct answer is C. While all of the choices listed could cause the pads to wear prematurely, the most common cause of this condition is when the rear shoes are incorrectly adjusted. Since the majority of braking action is done by the front brakes (especially on front-wheel-drive cars), it is imperative that the rear shoes are adjusted properly. This will help balance brake action as well as lining wear. Technician A says that DTCs can be accessed from any ABS system using flash diagnostics. Technician B says that ABS system tests can be performed with a bi- directional scan tool. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is B. Only a few ABS systems (primarily RWAL) offer flash code diagnostics for retrieving stored fault codes. A bi- directional scan tool can be used to perform tests on ABS system components. A technician can activate solenoids and valves while observing the change in that circuit. To determine if an intermittent ABS problem is related to an erratic wheel speed sensor signal, which of the following should be used? A. Ohmmeter B. Voltmeter C. Scan tool D. Digital storage oscilloscope - ANSWER-The correct answer is D. Answers B and C are incorrect because the sampling rates are too low. An intermittent can be seen with the digital storage oscilloscope (DSO) because it samples the electrical signal over 250,000 times per second. A few minutes after the engine was turned off on a vehicle with vacuum power assist, the brake pedal is applied and it is hard to push. Technician A says that this is a normal condition. Technician B says that the booster check valve is leaking. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is B. Technician A is incorrect because there should be at least one power assist before the pedal gets hard to push. Technician B is correct because the lack of power assist indicates that the check valve is leaking. During a brake inspection, an area of the vacuum brake booster below the master cylinder is found to be damp. Tech A says that this is a normal condition. Tech B says that any evidence of fluid indicates a leak and the master cylinder must be replaced. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is A. A small amount of fluid present here is normal due to the lubricating action of the master cylinder bore end seal. The brake fluid is kept from leaking back into the power booster by a seal on the pushrod. if a large amount of fluid is present, unbolt the master cylinder from the booster and look for signs of leakage. Technician A says that tapered roller bearings can be adjusted using a torque wrench. Technician B says that tapered roller bearings are adjusted using a dial indicator. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is C, both technicians are right. Both methods are commonly used to adjust tapered roller bearings. Consult the vehicle service manual for the specific adjustment procedure. All of the following could cause a pulsation to be felt in the brake pedal EXCEPT: A. Brake drum out of round B. Normal ABS operation C. lateral rotor runout All of the following can cause disc brake squeal EXCEPT: A. loose or missing anti-rattle springs B. Grease on the linings C. Glazed linings D. Dirt embedded in the linings - ANSWER-The correct answer is B. Brake linings that are contaminated with grease, oil, or brake fluid can cause the vehicle to pull when the brakes are applied, but would not cause the brakes to squeal. Technician A says that when rebuilding a caliper with a stroking seal, the condition of the caliper bore surface is critical. Technician B says that when rebuilding a caliper with a fixed seal, the condition of the piston surface is most important consideration. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is C, both technicians are right. A stroking seal is located in a groove in the caliper piston and moved with the piston. The lip of the seal rides against the surface of the caliper bore, so the caliper bore must be smooth to prevent leaks. A fixed seal is installed in a groove in the caliper bore. It seals against the outside surface of the caliper piston, so that surface must be in good condition to provide a good seal. All of the following can cause a vehicle to pull to one side when the brakes are applied EXCEPT: A. Seized caliper piston B. Worn strut rod bushings C. Blocked master cylinder compensating port D. Brake fluid-soaked linings - ANSWER-The correct answer is C. A blocked master cylinder compensating port could cause all brakes to drag but would not cause a brake pull. All of the other choices could cause brake pull. Technician A says that ABS wheel speed sensor gap should be adjusted with a non- magnetic feeler gauge. Technician B says that a paper spacer can be used to adjust abs wheel speed sensor gap but the paper must be removed before the vehicle is operated. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is A. New wheel speed sensors come with the paper spacer installed but it is not necessary to remove it; the spacer is designed to wear off during vehicle operation. When discussing wheel bearings, all of the following statements are true EXCEPT: A. Tapered wheel bearings are most commonly used on drive axles B. Sealed ball bearings are not adjustable. C. A new grease seal should be installed when bearings are repacked D. The races on tapered wheel bearings cannot be interchanged - ANSWER-The correct answer is A. Tapered roller bearings are usually used in non-drive axles. All of the other statements are true. All of the following could cause the parking brake to not hold a vehicle on a grade EXCEPT: A. Seized cables B. Excessive rear brake shoe-to-drum clearance C. Seized wheel cylinder D. Broken parking brake linkage - ANSWER-The correct answer is C. The parking brake system engages the rear brakes mechanically; a seized wheel cylinder would not affect parking brake operation. To determine the serviceability of a brake drum, all of the following should be checked EXCEPT: A. diameter B. minimum thickness C. out-of-roundness D. tape wear - ANSWER-The correct answer is B. Minimum thickness is checked when inspecting a disc brake rotor. All of the other measurements mentioned should be made when inspecting a brake drum. A vehicle's brake pedal is pumped rapidly 20 times and then held down. The master cylinder cover is then removed and when the pedal is released, a geyser is seen coming from the reservoir. Tech A says that this indicates that air is trapped in the system. Tech B says that this means that fluid is being forced out of the cylinder bore through the compensating ports and is normal master cylinder operation. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is A. Pumping the brakes compresses the air an d when the pedal is released, the compressed air pushes the hydraulic fluid back through the lines, causing it to squirt. Technician B is wrong because a small squirt of fluid should appear over the reservoir, indicating that fluid is being forced out of the cylinder bore through the compensating ports, only when the pedal is applied. Technician A says that RWAL ABS systems must be diagnosed using a scan tool. Technician B says that the abs arming light will only come on when there is a fault in the system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is D, neither technician is right. Technician A is wrong because, while most Rear Wheel Anti-Lock (RWAL) systems offer flash-code diagnostics, most four-wheel ABS systems require the use of a scan tool to extract stored fault codes from the computer's memory. Technician B is wrong Brake fluid leaking from a cracked brake line causes the brake light on the dashboard to come on in response to the loss of hydraulic pressure. Which of the following valves in the hydraulic system switched on the light? A. metering valve B. pressure differential valve C. proportioning valve D. residual check valve - ANSWER-The correct answer is B. The pressure differential valve and warning switch alerts the driver of a pressure loss in one of the hydraulic circuits. The residual check valve is often used in the master cylinder outlet port of a drum brake systems in order to maintain a slight pressure in the brake lines and wheel cylinders, which keep wheel cylinder piston tight against their bores. the metering valve delays front disc brake operation until the rear brakes shoes overcome the return spring tension. The proportioning valve is used to control rear brake pressers, particularly during hard stops. Technician A says that an integral ABS system is an add-on system. Technician B says that a non-integral ABS system is high-pressure system. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is D, neither technician is right. The non-integral ABS system is added on the vehicle's existing hydraulic brake systen, and is generally a low-pressure arrangement. The diameter of drums mounted on the same axle should measure within how many thousands of an inch of one another? A. 0.001 B. 0.005 C. 0.010 D. 0.020 - ANSWER-The correct answer is C. The diameter of brake drums mounted on the same axle must be withing 0.010-in. of one another. Absorption of 3% moisture can reduce the boiling point of DOT 3 brake fluid by what percentage? A. 10% B. 20% C. 25% D. 50% - ANSWER-The correct answer is C. Absorption of 3% moisture can reduce the boiling point of DOT 3 brake fluid by 25%. All of the following are procedures for removing air from a hydraulic system EXCEPT: A. Bench bleeding B. Power bleeding C. Manual bleeding D. Vacuum bleeding - ANSWER-The correct answer is A. Bench bleeding is a procedure for removing air from the master cylinder only. All of the other procedures remove air from the entire system. All of the following can be used to apply a non-directional finish to a disc brake rotor EXCEPT: A. Sanding block B. Fine file C. Lathe attachment D. Sanding disc - ANSWER-The correct answer is B. Files are not used to apply a non- directional finish on a disc brake rotor. All of the other methods can be used to give the rotor and swirl-like finish. All of the following can cause a problem in the Hydro-Boost system EXCEPT: A. Loose power steering pump B. Leaking power steering hoses C. Lower power steering pump pressure D. Leaking check valve - ANSWER-The correct answer is D. A vacuum check valve is used on a vacuum power booster. The Hydro-Boost system uses power steering pump fluid pressure rather than intake manifold vacuum, so all of the other choices would apply. A customer says that he has just replaced his front disc brake pads himself and now the abs warning light is on. Which of the following could be the cause? A. Damaged wheel speed sensor B. Incorrect wheel speed sensor gap C. Stuck ABS solenoid valve D. All of the above - ANSWER-The correct answer is D. Some common ABS problems can be caused by carelessness when performing basic brake service. Wheel speed sensors can be disturbed or damaged accidentally. Solenoid valves can stick if the caliper bleeder screws are not opened when the caliper pistons are retracted. Since the caliper is the lowest point in the system, dirt and corrosion naturally accumulate there. If the bleeder screws are not opened, brake fluid and these contaminants are forced backward into the system. When these contaminants find their way into the hydraulic control unit, they can cause valves to stick. Drum brake drag can be caused by all of the following EXCEPT: A. Frozen parking brake cables B. Frozen star wheel C. Restricted brake hose D. Swelled wheel cylinder cups - ANSWER-The correct answer is B. A frozen star wheel would not cause brake drag. Rather, it would prevent the automatic adjuster mechanism from working, which would gradually cause the brake shoe-to-drum clearance to increase as the linings wore. All of the other answers could cause the brake shoes to not retract from the drum, resulting in brake drag. first be manually or pressure bled and again after surge bleeding to make sure all air has been expelled. All of the following are cause for brake rotor refinishing EXCEPT: A. Hard spots B. Heat checks C. Scoring D. Thickness variation - ANSWER-The correct answer is A. Hard spots call for rotor replacement, since resurfacing seldom removes the entire hard spot. All of the other conditions can be corrected by machining, provided it can be done without machining past the minimum rotor refinishing thickness. The front disc brake pads are being replaced on a vehicle with composite rotors. The left front rotor is scored below the 'machine to' but not the ‘discard’ thickness. The right front rotor has minor heat checks but otherwise checks out OK. If cast rotors are the only available replacements, which of the following is the proper course of action? A. Machine both rotors, being careful not to exceed the ‘discard’ thickness. B. Replace the left front rotor and machine the right front. C. Replace both rotors. D. Replace the left front rotor and leave the right front alone. - ANSWER-The correct answer is C. Composite and cast rotors should not be mixed on the same axle. Answer A is wrong because, as the question indicated, the rotor is already worn past the ‘machine to' dimension. even if the rotor is not machined beyond the ‘discard’ thickness, this leaves no allowance for wear in the future. Which of the following brake symptoms can be caused by wheel bearing problems? A. Pedal pulsation B. Brake pull C. Grabbing D. All of the above - ANSWER-The correct answer is D. Loose whee! bearings can cause excessive rotor runout, which in turn can cause pedal pulsation. A failed wheel bearing seal can allow grease to contaminate the brake linings and cause brake pull and grabbing. Which component in the Hydro-Boost system provides power assist if there is a loss of hydraulic pressure to the system? A. Boost piston B. Check valve C. Accumulator D. Open-center spool valve - ANSWER-The correct answer is C. The accumulator can supply enough power assist for two stops if there is a loss of hydraulic pressure in the Hydro-Boost system. The boost piston provides the force to operate the master cylinder and the open-center spool valve regulates pump pressure. The check valve is used on vacuum operated boosters. A customer complains that the parking brake will not keep his car stationary. The car has four-wheel disc brakes. Technician A says that the caliper levers could be out of adjustment. Technician B says the brake shoes could need adjustment. Who is right> A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is C, both technicians are right. The brake must be inspected before reaching a diagnosis, but without knowing what type of system the car has, either technician could be right. There are two kinds of parking brakes on vehicles with rear disc brakes. One kind has small brake shoes inside a drum that is incorporated in the disc brake rotor. The shoes are forced against the drum by the linkage and cables in the same manner as conventional drum parking brakes. These shoes must be properly adjusted for the parking brake to work correctly. The other kind uses the rear disc brake pads. The linkage and cables actuate a cam or screw mechanism inside the caliper piston to push the caliper piston and pads against the rotor. Some of these systems require a caliper lever adjustment. When replacing an integral hub/bearing assembly on a front wheel drive vehicle, all of the following must be removed EXCEPT: A. Brake rotor B. Brake caliper C. Steering knuckle D. Wheel - ANSWER-The correct answer is C. The steering knuckle does not have to be removed when replacing an integral hub/bearing assembly. however, it must be removed when replacing the press-fit type front wheel bearing. A wheel cylinder has been disassembled and corrosion and light scoring have been found in the bore. Technician A says the bore can be refinished using a small hone lubricated with cutting oil. Technician B says oversize piston and cup seals can be installed if the hone removes too much material. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is D, neither technician is right. use only fresh clean brake fluid to lubricate the honing stones; never use petroleum=based cutting oil. After the cylinder has been hones, inspect it for excessive piston clearance. To check the maximum clearance, place a 0.003-in feeler shim lengthwise in the cylinder bore. if the piston can be inserted with the shim in place, the cylinder is oversize and cannot be rebuilt. Two technicians are discussing traction control systems. Technician A says that some traction control strategies do not use the brakes to control wheel spin. Technician B says that a fault in the ABS does not affect traction control. Who is right? A. Technician A only B. Technician B only C. Both A and B wheel studs determine the number of possible position to correct runout. This method requires little extra labor, no parts expense and no machining labor or expense. Resurfacing the rotor unnecessarily removes material and makes the rotor thinner, lessening its ability to absorb and dissipate heat and shortening the rotor's usable lifespan. New disc brake pads have just been installed. Technician A says the new pads must undergo a burnishing process during the road test to ‘cure’ the pads. Technician B says the new pads must be burnished to seat them on the rotor. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is C, both technicians are right. Whenever new brake pads are installed, they must undergo a burnishing, or break-in procedure before the vehicle can be operated normally. Burnishing accomplishes two things: it ‘cures’ the resin in the friction material, which could otherwise boil to the surface and cause glazing if the vehicle was immediately subjected to hard braking; and it ensures that the pads seat and make full contact with the rotor. The latter is particularly important if the rotors were not machined, since even a rotor that was deemed serviceable will not have a perfectly smooth surface. The parking brake pedal on a vehicle with automatic parking brake release remains depressed when the vehicle is placed in drive. All of the following are possible causes EXCEPT: A. defective vacuum motor B. faulty release switch C. vacuum leak D. seized cables - ANSWER-The correct answer is D. An automatic parking brake release mechanism releases the parking brakes when the automatic transmission is shifted into drive or reverse. These systems usually consist of a vacuum motor that is attached to a release lever, and a vacuum switch that routes vacuum to the motor when the transmission is placed in driver or reverse. When the driver selects the drive or reverse position, the switch directs engine vacuum to the vacuum motor, which releases the lever and the parking brakes. Seized cables could keep the vehicle from moving or cause sever drag, but would not keep the pedal from returning to the unapplied position. All of the other possibilities listed could keep the release lever from releasing the pedal, causing it to remain in the applied position. Two Technicians are discussing Electronic Stability Control (ESC) systems. Technician A says the ESC control module uses inputs from the steering wheel rotation sensor and wheel speed sensors to calculate the driver's intended path. Technician B says the ESC control module uses inputs from the lateral acceleration and yaw rate sensors to calculate the vehicle's actual path. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is C, both technicians are right. The ESC control program determines the driver's intentions using throttle and transmission data from Powertrain Control Module (PCM), wheel speed rate from the wheel speed sensors and steering wheel position and rate of movement input from the steering wheel rotation sensor. It compares this information with the input from the lateral acceleration and yaw rate sensors to determine if correction is needed. if the actual path the vehicle is traveling does not match the intended path, the control module applies brake pressure to individual wheels and/or reduces engine power to correct the motion of the vehicle. A vehicle exhibits intermittent ABS activation, but when the tech connects a scan too to the DLC, no DTS's are found. Which of the following could be the cause? A. damaged tone wheel teeth B. loose wheel bearing C. rust under the wheel speed sensor mount D. all of the above - ANSWER-The correct answer is D. False ABS activation occurs when the ABS is engaged even though none of the wheels are slipping. The ABS control module can interpret as weak or erratic wheel speed sensor signal as wheel slip and cycle the ABS at the affected wheel. Rust under the sensor mount loose wheel bearings and damaged tone wheel teeth can all affect the sensor gap, which in turn ca cause a weak or erratic signal. Technician A says as brake fluid ages, it can corrode ABS control valves. Technician B says brake fluid corrodes the copper in the brake lining. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B - ANSWER-The correct answer is B. At a slow rate, over several months of years, brake fluid slowly corrodes the copper in the inner lining of sleet brake tubing. The copper leaches into the brake fluid as ions, atoms with an electrical charge. When the corrosion inhibitors in the brake fluid eventually deplete, these copper ions become the oxidizer that corrodes ferrous metal parts the ABS control valves. Technician A is wrong because it is not the brake fluid that corrodes the ABS control valves, the rather the copper ions that are released by the brake fluid. Which of the following is the MOST correct wheel cylinder repair procedure? A. Disassemble, loosen the bleeder screw, clean and hone, clean and assemble B. Disassemble, clean and hone, clean and assemble, loosen the bleeder screw C. Loosen the bleeder screw, disassemble, clean and hone, clean and assemble D. Disassemble, clean and hone, loosen the bleeder screw, clean and assemble - ANSWER-The correct answer is C. Before rebuilding a wheel cylinder, first make sure that the bleeder screw can be loosened before disassembling the unit. if the bleeder screw brakes off, the wheel cylinder must be replaced. A vehicle's ABS warning light is on and a DTC for the left front wheel speed sensor is found in the computer's memory. When checked with an oscilloscope, the waveform for 
